The present invention relates to thermal energy converters and, more specifically, to thermoelements and thermopiles.
There is known a thermoelement comprising a substrate which is a thin plane of an insulating material with films of a semiconductor material arranged on both sides of said substrate at a certain distance therefrom, which films form thermoelectric branches of p- and n-type of conductivity, said branches being successively interconnected by means of commutation buses. In a thermopile based upon this thermoelement the buses extend to the end faces of the thermoelements.
In a thermopile employing thermoelements of the foregoing type, the task of arranging the maximum possible number of thermoelements over the substrate surface is achieved by forming the p- and n-type branches as long and narrow strips of semiconductor films.
In case of a temperature difference, electric current flows in such a thermopile along the thermoelement branches, passing from one branch to another through the commutation buses.
In the thermopile under review the thermoelement branches have a great intrinsic resistance due to their geometrical dimensions, because ##EQU1## WHERE R is the resistance of a branch,
.rho. is the resistivity of the semiconductor film, PA1 l is the length of the branch, and PA1 b and h are the width and thickness of the branch, respectively.
In the present case b&lt;1, and h&lt;&lt;1.
The fact that the width of a thermoelement branch is less than its length also reduces the reliability of the thermoelement, as there may appear cracks and ruptures in the active layer. A failure of one thermoelement results in a breakdown of the entire thermopile, as the thermoelements are interconnected in series. The thermoelement under review is further marked by considerable thermal and electric losses due to an insufficient contact surface between the active material (the film) and the commutation material (the commutation bus). A thermopile employing such thermoelements is marked by a low occupation factor of the substrate due to a great number of gaps between the branches.
It is the main object of the present invention to provide a thermoelement with a reduced intrinsic resistance of its branches.
It is another object of the present invention to provide a highly reliable thermoelement.
It is yet another object of the present invention to provide a thermoelement characterized by small thermal and electric losses for commutation.
Finally, it is an object of the present invention to provide a compact thermopile based upon such a thermoelement.
The main and other objects of the present invention are attained by providing a thermoelement comprising a substrate having semiconductor material films of n- and p-type of conductivity applied onto both sides thereof, which films form branches of said thermoelement interconnected by means of commutation buses. In the present thermoelement each branch consists, in accordance with the invention, of two semiconductor films of one type of conductivity, said films being applied one opposite the other onto the opposite sides of the substrate which has, over the portion thereof between the branches, a row of through holes, the commutation buses being arranged on both sides of said row and being electrically interconnected through said holes.
Such thermoelements are advantageous for producing a compact thermopile. The thermopile employing thermoelements of the above type must comprise a flexible substrate which must be accordian-pleated along the rows of through holes.
In the proposed thermoelement the width of a branch is greater than the length thereof, which substantially reduces the intrinsic resistance of the thermoelement and, consequently, of the thermopile wherein such thermoelements are employed. The foregoing factor also accounts for an increased operational reliability of the thermoelement. In addition, due to the fact that each branch of the thermoelement consists of two parallel films, a failure of one film does not lead to a breakdown of the thermoelement itself.